1. Field of the Invention
The invention relates to a yarn delivery device for textile machines, and more particularly to a yarn delivery device with a drivable storage drum.
2. Discussion of Relevant Art
Yarn delivery devices with the abovementioned features of a yarn storage drum are known, for example, from DE-PS 35 01 944 German Granted Patent!. In this yarn storage drum, the yarn to be processed is taken up tangentially, in multiple wraps, by a yarn takeup region of frustroconical shape, and is then transferred to a yarn storage region which is adjacent to, and of lower conicity than, the yarn takeup region. By means of this shape and the multiple turns, the result is attained that the yarn can, on the one hand, be supplied to the yarn processing location of the textile machine at the peripheral speed of the yarn storage drum, without slip, and on the other hand that the yarn is laid down parallel and adjacent, without overwinding and, because of the conicity of the yarn storage region, makes possible a longitudinal displacement of several yarn turns downwards in the axial direction.
When yarn is taken from a supply bobbin in order to be supplied to a needle for the formation of a stitch, tension peaks can occur which can propagate as far as the stitch formation. Such tension peaks can arise, in the case of multifilament yarns, due for example to filaments projecting outwards from the last layer so that these filaments hook onto the filaments of the yarn to be taken off, in the manner of a hook and loop fastener. The yarn to be taken off can thereby remain held for a short time. The resulting tension peaks are disadvantageous, particularly in stitch formation, since the stitch can be made too small due to such a tension peak, so that the relatively thick head of the needle can no longer pass through. This can lead to a machine stoppage.
A minimal reduction can be provided by the construction of the frustroconical yarn takeup region, and below it a substantially cylindrical yarn takeoff region; but this is however not sufficient in practice to make possible a sufficient decrease in the tension peaks, even when the processing of different materials is required, such as for example cotton, wool, synthetic fiber materials, and the like, so that a reliable and uniform stitch formation of a knitted fabric can be provided.